Progress in FY 2005 has been in the following areas: (1) We have continued structural studies of amyloid fibrils. We have determined a number of quaternary contacts in amyloid fibrils formed by the Alzheimer's beta-amyloid peptide, using new solid state NMR methods. This allows us to develop a revised structural model for beta-amyloid fibrils, in which all basic aspects of the structure are determined by experimental data. This model applies to fibrils grown with gentle agitation. We have also developed improved techniques for preparing beta-amyloid fibrils under quiescent conditions, such that the fibrils have homogeneous morphologies and clean NMR spectra. Structural characterization of this alternative fibril form is under way. We have also begun structural studies of fibrils formed by the islet amyloid precursor protein (a.k.a. amylin). In our amylin project, we have developed efficient protocols for synthesizing and purifying the peptide, as well as protocols for preparing fibrils with uniform morphologies and high-quality solid state NMR spectra. (2) We have continued structural studies of a 40-residue peptide from HIV-1 Vpu, containing its transmembrane segment, in phospholipid bilayers. Using a novel form of two-dimensional solid state NMR, we have identified intermolecular contacts between transmembrane helical segments in Vpu oligomers. These contacts allow us to develop experimentally-based models for the supramolecular structure of oligomeric Vpu ion channels. (3) We have developed new solid state NMR methods, including a new approach to selective measurement of specific interatomic distances between carbon-13 labels in samples that contain uniformly-labeled amino acids. This new approach to selective distance measurements seems likely to facilitate a wide range of structural studies by solid state NMR. In addition, we have made significant progress on the design, construction, and initial demonstration of a new ultra-low-temperature solid state NMR probe with magic-angle spinning capabilities. This new solid state NMR probe promises to improve the sensitivity of solid state NMR measurements by a factor of 10 or more.